1. Field of the Invention
The present invention generally relates to a storage device and a method; in particular, to a memory storage device and a control method thereof.
2. Description of Related Art
Non-volatile memory (also referred as non-electrically dependant memory) can be used in data storage, which is generally applied in various storage devices, such as a memory card, USB thumb drive, Solid State Drive (SSD) and so on. Flash memory demonstrates advantages of, for example, high storage density, low power consumption, effective access efficiency, and reasonable manufacturing cost, thereby allowing itself to play the major role in current non-volatile memory development.
Typically, common non-volatile memory entirely utilizes Multi-Level-Cell (MLC) memory or Single-Level-Cell (SLC) memory, wherein a memory composed of MCL is known as high density memory, and a memory composed of SCL is known as low density memory. Compared with the low density memory, the data storage capacity per unit area in the high density memory may increase multiple times, hence providing advantages of greatly enhanced storage capacity and cost reduction, but whose required time for data read/write operations, programming processes, and erase actions is longer; furthermore, MLC process technologies result in less erase cycles that can be endured by a high density memory, thus collaterally affecting the data access speed and life span of the storage devices using the high density memory.
In view of the features of large storage capacity and low cost found in the high density memory, but having slower data access rate and less endurance counts, whereas the low density memory providing the features of faster data access rate and more endurance counts with smaller storage capacity and higher manufacturing cost, accordingly a type of memory formed by the aforementioned two densities of memories in one single storage device is developed, referred as the hybrid density memory.
At present, the storage device comprising the hybrid density memory commonly available in the industry usually records more frequently used data by means of the low density memory, while recording less frequently used data with the high density memory; however, in regard to the limited storage capacity of the low density memory, planning of the approaches for new/old data processes may affect the operation performance of the hybrid density memory storage device; besides, since there exist differences in the erasure counts that memory of different density can possibly endure, and upon update or access to the data stored in the memory, the block holding the data will be erased, therefore further leading to uneven erasure results in these two types of memory having different density, so that it is accordingly inevitable to confront upon a scenario that the memory of one density may reach the endurance count limit first, while the memory having the other density is still operable, thus undesirably ending prematurely the life span of the storage device.